If you're right, don't you think this wouldn't be an issue for anyone? Reality of what people have claimed and believe seems to go against what you're suggesting.
Their point shows that it isn't actually relatability, as in the inherent nature of the creature being described. It is, instead, purely within the heart and mind of the speaker: this is
unfamiliar, so I can't relate; this is not
long-established, so I can't relate; this is too
monstrous, so I can't relate; etc.
Which is precisely what creates the infuriating catch-22 that Hussar, myself, and others have described: anything novel is "unrelatable," that is,
unfamiliar so it won't ever get the chance to be displayed, so it can't develop new tradition, so it can't
become familiar(=relatable). And thus we are stuck with damn near every setting being massively humanocentric. Folks mentioned BG3 earlier, and frankly, it's goddamn hilarious anyone thinks that such a setting
isn't humanocentric. The
vast majority of characters you deal with are human, elf/half-elf, dwarf, or halfling, other than the tiefling refugees...and the
fact that they're tiefling refugees is very specifically used against them by racist buttholes in-game. (While the writers do make it pretty clear that this is an immoral and bigoted thing to do, many such racist jerks get away with it without any repercussions whatsoever.) Faerûn is
absolutely a humanocentric setting, it's just soft humanocentrism rather than the much harder and active, overt humanocentrism of Greyhawk.
You see both of these things, the conflation of inherent nature with personal response and the catch-22 effect, applied to
all sorts of things in the D&D space. It's deeply infuriating.